{
  "author": "ckeller@fusioncybersecurity.us",
  "cat": "New Code Atypical Path",
  "detect": {
    "event": {
      "FILE_PATH": "C:\\Windows\\Temp\\3A22930E-7933-4932-A06B-DA4B7DB2FB1F\\MpSigStub.exe",
      "HASH": "935c8fb7d58e4845dec66063f67f623afa5cbfeccbd6eca726fecab21e362030",
      "PROCESS_ID": 17988
    },
    "routing": {
      "arch": 2,
      "did": "",
      "event_id": "00647866-2ff6-4248-9830-71d35352d10a",
      "event_time": 1774468114361,
      "event_type": "NEW_DOCUMENT",
      "ext_ip": "23.128.32.10",
      "hostname": "desktop-3nfb237",
      "iid": "b2cd59fc-d09d-49e0-a9f2-1fd79ee9c175",
      "int_ip": "192.168.50.40",
      "latency": 6382,
      "moduleid": 2,
      "oid": "d3541070-8b0e-4663-8a6a-aa0727aacd36",
      "parent": "9727bc761f07cc5e5c90b93a69c43c07",
      "plat": 268435456,
      "sid": "ed8f7c3f-3a1a-493e-8fa4-35eb8c30b136",
      "tags": [
        "fusion-soc-alert",
        "fusion-soc-case",
        "fusion-soc-pulled",
        "fusion-soc-triage",
        "fusionsoc-critical",
        "fusionsoc-high",
        "fusionsoc-investigated",
        "qucikbooks",
        "windows",
        "yara_detection_memory"
      ],
      "this": "88b048d207538b2cf3cd029569c43c17"
    }
  },
  "detect_id": "71bf5aa6-3cfe-4bc4-8b2e-413369c43c18",
  "gen_time": 1774468120743,
  "link": "https://app.limacharlie.io/orgs/d3541070-8b0e-4663-8a6a-aa0727aacd36/sensors/ed8f7c3f-3a1a-493e-8fa4-35eb8c30b136/timeline?time=1774468114\u0026selected=88b048d207538b2cf3cd029569c43c17",
  "namespace": "general",
  "routing": {
    "arch": 2,
    "did": "",
    "event_id": "00647866-2ff6-4248-9830-71d35352d10a",
    "event_time": 1774468114361,
    "event_type": "NEW_DOCUMENT",
    "ext_ip": "23.128.32.10",
    "hostname": "desktop-3nfb237",
    "iid": "b2cd59fc-d09d-49e0-a9f2-1fd79ee9c175",
    "int_ip": "192.168.50.40",
    "latency": 6382,
    "moduleid": 2,
    "oid": "d3541070-8b0e-4663-8a6a-aa0727aacd36",
    "parent": "9727bc761f07cc5e5c90b93a69c43c07",
    "plat": 268435456,
    "sid": "ed8f7c3f-3a1a-493e-8fa4-35eb8c30b136",
    "tags": [
      "fusion-soc-alert",
      "fusion-soc-case",
      "fusion-soc-pulled",
      "fusion-soc-triage",
      "fusionsoc-critical",
      "fusionsoc-high",
      "fusionsoc-investigated",
      "qucikbooks",
      "windows",
      "yara_detection_memory"
    ],
    "this": "88b048d207538b2cf3cd029569c43c17"
  },
  "source": "d3541070-8b0e-4663-8a6a-aa0727aacd36.b2cd59fc-d09d-49e0-a9f2-1fd79ee9c175.ed8f7c3f-3a1a-493e-8fa4-35eb8c30b136.10000000.2",
  "source_rule": "general.NEW FILE WRITE BYTES SAMPLE GRAB",
  "ts": 1774468120000
}

{
  "virustotal": {
    "malicious": false,
    "provider": "virustotal",
    "reputation": 0,
    "stats": {
      "confirmed-timeout": 0,
      "failure": 0,
      "harmless": 0,
      "malicious": 0,
      "suspicious": 0,
      "timeout": 0,
      "type-unsupported": 4,
      "undetected": 72
    }
  }
}

{
  "confidence": 0.95,
  "false_positive_reason": "Legitimate system process (Windows Defender update) running from an expected temporary location.",
  "investigation_questions": [
    "Is the binary digitally signed by Microsoft?",
    "Are there any other suspicious processes running on this host at the same time?"
  ],
  "ioc_analysis": "The hash (935c8fb7d58e4845dec66063f67f623afa5cbfeccbd6eca726fecab21e362030) has a clean reputation on VirusTotal (0/72) and is identified as the legitimate MpSigStub.exe binary. The file path C:\\Windows\\Temp\\3A22930E-7933-4932-A06B-DA4B7DB2FB1F\\MpSigStub.exe is a standard staging location for Microsoft updates.",
  "iocs_extracted": [
    "935c8fb7d58e4845dec66063f67f623afa5cbfeccbd6eca726fecab21e362030",
    "C:\\Windows\\Temp\\3A22930E-7933-4932-A06B-DA4B7DB2FB1F\\MpSigStub.exe"
  ],
  "mitre_techniques": [
    "T1036"
  ],
  "recommended_actions": [
    "Close case as false positive (unanimous AI verdict)",
    "No action required",
    "Consider tuning the rule to exclude signed Microsoft binaries in C:\\Windows\\Temp\\ to reduce noise"
  ],
  "risk_score": 7,
  "severity": "low",
  "summary": "**Vote: UNANIMOUS (3/3 -\u003e FALSE POSITIVE)**\n\n### \u264a gemini-cli Analysis (Primary)\n**Verdict:** false_positive | **Confidence:** 1.0\nThe detection triggered on a legitimate Microsoft Windows Defender binary, MpSigStub.exe, being written to a temporary directory. This is a common occurrence during Defender signature updates and aligns with historical false positive patterns for this rule.\n\n**IOC Analysis:** The hash (935c8fb7d58e4845dec66063f67f623afa5cbfeccbd6eca726fecab21e362030) has a clean reputation on VirusTotal (0/72) and is identified as the legitimate MpSigStub.exe binary. The file path C:\\Windows\\Temp\\3A22930E-7933-4932-A06B-DA4B7DB2FB1F\\MpSigStub.exe is a standard staging location for Microsoft updates.\n\n---\n\n### \ud83e\udd16 qwen3.5:4b Analysis (Secondary + RAG)\n**Verdict:** false_positive | **Confidence:** 0.95\nThe detection flagged a legitimate Windows Defender binary (MpSigStub.exe) executing in a temporary directory during signature updates. Historical feedback and investigation results confirm this is a common benign occurrence for Microsoft-signed system processes.\n\n**IOC Analysis:** MpSigStub.exe is a known Microsoft-signed component used by Windows Defender to update signatures. Its execution from C:\\Windows\\Temp\\ is standard behavior during maintenance cycles, and the process tree shows no suspicious child processes or anomalous command-line arguments.\n\n---\n\n### \ud83e\udd16 deepseek-r1:8b Analysis (Secondary + RAG)\n**Verdict:** false_positive | **Confidence:** 0.9\nThe detection is a false positive as MpSigStub.exe is a legitimate Microsoft-signed binary associated with Windows Defender ATP, commonly written to temporary directories during signature updates.\n\n**IOC Analysis:** FILE_PATH: C:\\Windows\\Temp\\3A22930E-7933-4932-A06B-DA4B7DB2FB1F\\MpSigStub.exe is atypical but legitimate for Windows Defender operations. HASH: 935c8fb7d58e4845dec66063f67f623afa5cbfeccbd6eca726fecab21e362030 is likely Microsoft-signed, confirmed by investigation and IOC validation rules.",
  "verdict": "false_positive",
  "voting": {
    "auto_action": "auto_close_fp",
    "mode": "unanimous",
    "total_models": 3,
    "vote_summary": [
      "gemini-cli: false_positive (low, 100% confidence)",
      "qwen3.5:4b +RAG: false_positive (informational, 95% confidence)",
      "deepseek-r1:8b +RAG: false_positive (low, 90% confidence)"
    ],
    "votes": [
      {
        "confidence": 1.0,
        "model": "gemini-cli",
        "verdict": "false_positive"
      },
      {
        "confidence": 0.95,
        "had_rag": true,
        "model": "qwen3.5:4b",
        "verdict": "false_positive"
      },
      {
        "confidence": 0.9,
        "had_rag": true,
        "model": "deepseek-r1:8b",
        "verdict": "false_positive"
      }
    ],
    "winning_count": 3,
    "winning_verdict": "false_positive"
  }
}